1. Field of the Invention
The present invention generally relates to filters used to remove acids, water, particles and other material from fluids and, more particularly, the present invention relates to a filter assembly adapted for use with turbomachinery for filtering fluid flow passing through such turbomachinery.
2. Description of Related Art
Filter elements are used for the removal of various impurities from fluids and have different configurations depending on the desired application. Cylindrical filter elements having radially-extending, longitudinal pleats are a common type of filter element used to filter both liquids and gases. In a typical cylindrical, pleated filter element, a plurality of pleats is arranged around a tubular core to define a cylinder. Although pleated filter elements having this configuration may be efficient in removing particulate matter from fluids, such as removing particulate matter from water or oil, common filter elements do not have the capability of removing other harmful byproducts, such as acids.
In the power generation industry, turbine bearings require a substantial amount of lubrication during operation. Such lubrication often takes the form of synthetic hydraulic oil, because of the need for fire resistance. One example of such a fluid is phosphate ester. It is common for phosphate ester based fluids to chemically break down and produce acids over use and time. For this reason, acid absorbing cartridges are used to filter acid from the synthetic hydraulic oil used in turbomachinery. Cartridges containing fullers earth or activated alumina are commonly used for this purpose. However, both fullers earth or activated alumina have the disadvantage of forming chemical precipitates in the fluid, which can be detrimental to the system. Ion exchange resins are synthetic polymers capable of combining or exchanging ions in a surrounding solution. Ion exchange filters and resins are disclosed in U.S. Pat. No. 6,200,471 to Nohren, Jr.; U.S. Pat. No. 6,113,784 to Stoyell et al.; U.S. Pat. No. 6,197,193 to Archer; U.S. Pat. No. 5,094,745 to Reynolds; and U.S. Pat. No. 4,277,332 to Baughn, which are incorporated herein by reference.
Ion exchange resins can remove acid more efficiently than fullers earth or activated alumina, and without the addition of detrimental chemical precipitates. Ion exchange resins are commonly used in water based fluids, but have only recently been employed for acid removal in hydraulic and lubrication oils. The reason for this is that ion exchange resins naturally contain water, which is detrimental to hydraulic and lubrication oils. For this reason, the use of ion exchange resin filters typically requires additional costly equipment, such as vacuum dehydrators, which are not economically feasible for smaller scale applications.
Acid is not the only contaminate that can degrade the suitability of turbomachinery lubricants. Water can degrade a fluid's lubricity, and particulate matter can damage system components. Additionally, both water and particulate matter act as catalysts in the chemical reactions that form acids in phosphate ester fluids.